Blasting initiator



Sept. 9, 1941. P. L. SALZBERG 2,255,600

-BLASII;ING INITIATOR Filed Aug. 5, 1-938 Paul Safyezzg:

' INVENTOR.

ATTORNEY tective coating results.

Patented Sept. 9, 1941 UNI TED STATES- PATENT OFFICE BLASTING INITIA'I'OB Paul Lawrence Salzberg, Carrel-oft, Del, assignor to E. I. du Pont de Nemonrs a Company, Wilmlngto 11, Del., a corporation of Delaware Application August 3, 1938, Serial No. 222,835

15 Claims.

The present invention relates to new and improved blasting initiators and more particularly to an improved shell for the same.

As is well known in the art of blasting initiator manufacture, it has been necessary to avoid the use of certain types of shells in combination with particular classes of explosive compounds, due to the recognized incompatibility of said shell materials with charges containing said explosive compounds. In particular, certain explosive compounds react with shell materials to form dangerously sensitive substances. For example,

shells containing copper are incompatible with explosive charges containing azides, especially lead azide. This is believed to be due to the reaction of copper with lead azide to. form the dangerously sensitive copper azide. At any rate it is particularly disadvantageous that the highl desirable standard gliding metal shell, a copper-zinc alloy of high copper content, has never been successfully employed in conjunction with charges containing lead azide.

The object of this invention is a new'and improved blasting initiator. A further object is a blasting initiator shell compatible with certain reactive explosive charges. An additional object is a blasting initiator. provided wlth a shell of a .metal not ordinarilycompatible with lead azide,

sition having a mercaptan group; The shell thus treated may be employed in the manufacture of 'a safe blasting initiator containing explosive charges notcompatible with copper, for example, lead azide. According to my invention, the entire surface of the blasting cap shell is exposed to the action of the mercaptan. whereby a pro- This protective coating affords complete and uniform coverage, and has no tendency to become displaced.

Although mercaptans in general produce a desirable coating for metal shells, I prefer to use those characterized'by a long-chain structure, as,

- for example, lauryl mercaptan (l-dodecanethiol), octyl mercaptan, or cetyl mercaptan (l .-hexa decanethiol) These longer-chain compounds produce-a film of superior quality.

tans combine chemically with the copper present in the shell, the reactive end of the mercaptan structure attaching itself to the metal surface, leaving a non-reactive film, the thickness of which is proportional to the length of the chain. This is believed to prevent formation of the highly sensitive azide which is considered to be formed ordinarily by the reaction between moisture, lead azide and copper, supposedly through the hydrolysis of the azide and hydrazoic acid 'and further reaction oi the latter with the copper. It is suflicient that copper shells treated with the mercaptan, according to my invention, are entirely satisfactory when employed with charges containing lead azide.

In carrying out my invention, my protective coat-forming composition, as hereinbefore mentioned, is added to such quantity of solvent that I a solution of the desired concentration results. This solution may be applied to the blasting cap shell according to any of the commonly known inethods for the application of protective coatngs, One method which requires only a short time, but which has proved effective, is the tumbling barrel method of treatment. The shells to be treated are first cleaned in order to remove any film which might retard or prevent the action of the' mercaptan. The cleaning agents employed are those in common usage for such purposes, for example, solvents such as acetone, alcohol, etc., or certain dilute mineral acids. After cleaning and drying, the shells are rumbled in a barrel containing a solution of the merca'ptan in a suitable solvent. r

The following examples are given in order to illustrate this preferred 'method of operation.

Example I A 5% solution of lauryl mercaptan in benzene was introduced into a tumblingbarrel. Blasting cap shells of gilding metal were then added, and the barrel rumbled for one hour. At the end of this period the shells were removed, the excess liquid drained, and the remaining liquid permitted to evaporate. When dry, the; shells were characterized by a film-like coating nonreactive with respect to hydrazoic acid.

Example II Separate solutions of lauryl mercaptan, octyl mercaptan and mercaptobenzothiazole were employed to coat numerous gliding metal shells. The lauryl mercaptan and octyl mercaptan' were dissolved in benzene to form 5% solutions, where- According to one theory alt/least, the mercapas the mercaptobenzothiazole was in the form of shells with similar explosive compositions, in-

eluding lead azide, and subjecting the loaded shells to an atmosphere of approximately 100% humidity. The shells were inspected at regular intervals, tests being made in order to detect the presence of copper azide. The results obcopper-tin, for example. Furthermore, although my invention has been described particularly with respect to lead azide, it is understood that the general .concept will be. applicable. to any shell material with respect to any initiator. charge when neither is detrimentally reactive with mercaptan, where incompatibility otherwise would exist between said charge and said shell material; I intend, therefore, to be limited only in accordance with the following claims.

I claim: v

1. A blasting initiator comprising a mercaptan-treated metal shell, and in said shell an explosive charge incompatible with said metal.

tained are shown in the following tabulation. 2. A blasting initiator comprising a mercap- Mercapto- Lauryl Storage Octyl mercaptan Untreated Ms ases. MS

1 month Negative test.

2 months.

8 months.

The various mercaptans described hereinbe fore are given merely as specific embodiments and should not be construed as limiting my invention. Other mercaptans having a long chain structure have been found equally desirable, cetyl mercaptan, for example.

The invention may be understood more readily by referring to the drawing which is a view of a blasting initiator shell provided with a coating of mercaptan, as described by the legends.

My invention, therefore, discloses an initiator that is new to the art, together with a process for making the same. The process employed for treating the initiator shell is characterized by simplicity and ease of application of the coating material. The adoption of the novel initiator permits the use of lead azide, as an explosive charge, particularly in any blasting caps, ordinary fuse-type or electrical, 'which are not moisture-proof, without necessitating an initiator shell free from copper. On the contrary, the lead azide may be charged directly into the treated copper-containing shell without danger that sensitive compounds will be formed. In addition, the mercaptan-treated copper shells are more resistant to corrosion than untreated shells.

From the foregoing description of my invention, it is apparent that many variations may be made without departing from the spirit and scope thereof. Although the discussion has been directed particularly toward gilding metal because this metal has been commonly employed, yet my invention is not limited to said gilding metal, but is applicable when any shell having a significant copper content is employed, as alloys of Positive test.

som

tan-treated, copper-containing shell and in said shell an explosive charge incompatible with copr. 3. A blasting cap comprising an explosive charge including lead azide .in a mercaptantreated, copper-containing cap shell.

4. The blasting cap of claim 3, wherein the mercaptan employed is 'octyl mercaptan.

5. The blasting cap of claim 3, wherein the mercaptan employed is l-hexadecanethiol.

6. The blasting cap of claim 3, wherein the mercaptan employed is mercaptobenzothiazole.

'7. A blasting cap of the fuse-type containing an explosive charge comprising lead azide, said charge being contained in a mercaptan-treated, copper alloy cap shell.

8. A fuse-type blasting cap comprising a mercaptan-treated, copper-containing shell.

9. A process for treating copper-containing initiator shells, which process comprises subjecting said shells to the action of a solution consisting substantially of along chain mercaptan.

sive charge including lead azide enclosed in a' mercaptan-treated, copper-containing cap shell.

PAUL LAWRENCE SALZBERG. 

